Rolex introduced the Syloxi Hairspring for their ladies models in 2014. The hairspring and balance wheel, shown in the photo below, help regulate the oscillations of the movement. The hairspring must be resistant to shocks, spikes in temperature and magnetism to ensure the precision of the timepiece. 

Rolex's Syloxi Hairspring (photo: Rolex/Christophe Lauffenburger)

The use of silicon for the hairspring is a patented innovation that substantially improves the performance of the oscillator as compared to traditional ferromagnetic hairsprings. The patent itself covers the unique characteristics of this hairspring. The silicon and silicon oxide composite used is the first part of the patent. The geometry that optimizes the isochronism and its chronometric regularity is also part of it. There is also a patent for the way that Rolex fixes the end of the hairspring to the balance staff and the balance bridge, enhancing its flatness and concentricity. 

Rolex utilizes a high-precision manufacturing process known as deep reactive ion etching (DRIE) to make the Syloxi Hairspring. It was introduced in their 2236 movement, manufactured in-house by the watchmaker for their women's watches. This increases its power reserve to approximately 55 hours. 

>>BACK TO TECH